Brake system for a vehicle train and tractor therewith

Abstract

A fluid-operated braking system ( 1 ) for a tractor-trailer vehicle includes a trailer control valve ( 2 ), a parking brake module ( 3 ), and an electronic control unit ( 4 ) electrically connected to the trailer control valve ( 2 ) and to the parking brake module ( 3 ). A pressure fluid accumulator ( 13 ) of the braking system ( 1 ) is connected to a control pressure input (P 43 ) of the trailer control valve ( 2 ). A redundancy circuit controls the control pressure input (P 43 ), even during a malfunction of the control unit ( 4 ). The parking brake module ( 3 ) includes a control valve ( 14 ), a redundancy valve ( 15 ) and a changeover valve ( 16 ) controlled by an electronic switch unit ( 20 ) with a holding function. When the control unit ( 4 ) malfunctions, the last error-free switching position of the control valve ( 14 ) or the redundancy valve is maintained until a operationally safe resting state is reached or the ignition system is switched off.

The invention claimed is: 
     
       1. A braking system ( 1 ) for a motor vehicle including a tractor vehicle with a tractor vehicle brake and a trailer vehicle ( 5 ) with a trailer brake ( 6 ), the tractor vehicle having an ignition system for a drive engine of the tractor vehicle energized by an electrical energy accumulator of the tractor vehicle, wherein the braking system ( 1 ) is fluid operated, comprising:
 a trailer control valve ( 2 ) and a parking brake module ( 3 ) which are electrically controllable, 
 an electronic control unit ( 4 ) for the control of the trailer brake ( 6 ) of the trailer vehicle ( 5 ), electrically connected to the trailer control valve ( 2 ) and to the parking brake module ( 3 ), 
 the parking brake module ( 3 ) being fluid-connected at the input side to a pressure fluid accumulator ( 13 ) of the braking system ( 1 ) of the motor vehicle and at the output side to a control pressure input (P 43 ) of the trailer control valve ( 2 ) for selectively pressurizing or depressurizing the control pressure input (P 43 ) of the trailer control valve ( 2 ), and 
 the parking brake module ( 3 ) having a redundancy circuit for pressurizing or depressurizing the control pressure input (P 43 ) of the trailer control valve ( 2 ) even during a malfunction or a failure of the electronic control unit ( 4 ), 
 wherein the parking brake module ( 3 ) includes 
 a first directional valve configured as a control valve ( 14 ), 
 a second directional valve configured as a redundancy valve ( 15 ), and 
 a pressure-controlled changeover valve ( 16 ), 
 wherein the control valve ( 14 ) and the redundancy valve ( 15 ) have input sides that are respectively fluid-connected to the pressure fluid accumulator ( 13 ) and output side that are respectively fluid-connected to a respective one of two inputs (P 17 , P 18 ) of the changeover valve ( 16 ), 
 one output (P 19 ) of the changeover valve ( 16 ) being fluid-connected to the control pressure input (P 43 ) of the trailer control valve ( 2 ) so that an input pressure at one or both inputs (P 17 , P 18 ) of the changeover valve ( 16 ) can be passed through to the control pressure input (P 43 ) of the trailer control valve ( 2 ), 
 wherein the control valve ( 14 ) is switchably connectable via a first electrical switching device ( 18 ) to the electrical energy accumulator of the tractor vehicle, 
 wherein the redundancy valve ( 15 ) is switchably connectable via a second electrical switching device ( 19 ) to the electrical energy accumulator and to the ignition system of the tractor vehicle, 
 wherein, in a first switching position of at least one of the control valve ( 14 ) and the redundancy valve ( 15 ), the pressure fluid accumulator ( 13 ) is blocked off from the control pressure input (P 43 ) of the trailer control valve ( 2 ) and in a second switching position of the control valve ( 14 ) and/or the redundancy valve ( 15 ) the pressure fluid accumulator ( 13 ) being fluid-connected to the control pressure input (P 43 ) of the trailer control valve ( 2 ), 
 wherein the electronic control unit ( 4 ) includes an electronic switch unit ( 20 ) with a holding function, 
 wherein the redundancy valve ( 15 ) and the control valve ( 14 ) are electronically interconnected via the switch unit ( 20 ) and the redundancy valve ( 15 ) is controllable by the switch unit ( 20 ), 
 wherein the holding function is configured to store a respective currently assumed first switching position or second switching position of the redundancy valve ( 15 ) or of the control valve ( 14 ), 
 and wherein, during a recognized malfunction or a failure of the electronic control unit ( 4 ), the most recently stored first switching position or second switching position of the control valve ( 14 ) or the redundancy valve ( 15 ), which was stored during a normal error-free operation of the electronic control unit, is maintained until the earlier one of the electronic control unit ( 4 ) switching to an operationally safe resting state or the ignition system being switched off. 
 
     
     
       2. The braking system according to  claim 1 , wherein the control valve ( 14 ) and the redundancy valve ( 15 ) are configured as 3/2-way, normally closed directional valves which are electromagnetically actuatable. 
     
     
       3. The braking system according to  claim 1 , wherein the control valve ( 14 ) and the redundancy valve ( 15 ) are switchable independently of each other in the normal error-free operation of the electronic control unit ( 4 ). 
     
     
       4. The braking system according to  claim 1 , wherein the first electrical switching device ( 18 ) and the second electrical switching device ( 19 ) have mutually decoupled electrical circuits for supplying electrical power to the control valve ( 14 ); and the redundancy valve ( 15 ), the control valve ( 14 ) being assigned a first high-side switch ( 18   a ), which connects a magnetic circuit of the control valve ( 14 ) switchably to the electrical energy accumulator, the control valve ( 14 ) being assigned a first low-side switch ( 18   b ), which connects the magnetic circuit of the control valve ( 14 ) switchably to ground, and the redundancy valve ( 15 ) being assigned a second high-side switch ( 19   a ), which connects the magnetic circuit of the redundancy valve ( 15 ) switchably to the ignition system and to the electrical energy accumulator of the tractor vehicle, and the redundancy valve ( 15 ) being assigned a second low-side switch ( 19   b ), which connects a magnetic circuit of the redundancy valve ( 15 ) switchably to ground. 
     
     
       5. A motor vehicle, such as a farming tractor vehicle and trailer combination, a semitrailer, or a platform road train, comprising a braking system according to  claim 1 .